The present invention relates to a cylinder lock that is used for doors of vehicles, buildings and the like, and particularly relates to a cylinder lock that cannot be unlocked, by slipping of a cylinder, in the event that a screwdriver, an unauthorized key or the like is inserted and is forcibly turned.
In this type of cylinder lock, insertion of an authorized key into a cylinder including tumblers engaged with lock grooves formed in a sleeve causes the tumblers to be drawn into the cylinder and allows the cylinder to be turned to a locked position or an unlocked position. The cylinder lock, however, may improperly be unlocked with the tumblers destroyed in event that a screwdriver, an unauthorized key or the like is inserted into the cylinder and is forcibly turned, even though the tumblers are engaged with the lock grooves of the sleeve.
There have conventionally been proposed cylinder locks having a configuration in which a cylinder is freely turned (slipped) together with a sleeve relative to a holder on occasion of such improper unlocking. Prior art associated with this type of the cylinder lock is hereinafter described.
[Patent Document 1] JP 3076920 B
[Patent Document 2] JP 3380611 B
In Patent Document 1 is disclosed a cylinder lock in which a sleeve, a cam body, and a clutch mechanism are provided between a holder and a cylinder. The sleeve is provided between the holder and the cylinder so that the sleeve is capable of turning in circumferential directions and advancing and retreating in axial directions. In the sleeve are formed lock grooves with which a plurality of tumblers provided in the cylinder are engaged. On an inner circumferential surface of the sleeve is formed a ring groove into which a protruded portion provided on the cylinder is rotatably inserted. The cam body makes the sleeve advance or retreat with a turn of the sleeve. The clutch mechanism has a joint member in pressure contact with an end of the sleeve on the advancing side, connects the cylinder to the rear rotor with displacement of the joint member that is caused by retreat of the sleeve, and positions the protruded portion of the cylinder in the ring groove of the sleeve. The clutch mechanism disconnects the cylinder from the rear rotor with displacement of the joint member that is caused by advancement of the sleeve, and positions the protruded portion of the cylinder in the lock grooves of the sleeve. In the event that unlocking of the cylinder lock is attempted with use of tools such as an unauthorized key and a screwdriver, the clutch mechanism is switched to a disconnected state with advancement of the sleeve. Thus the force applied to the cylinder is not transmitted to the rear rotor, and a locked state is maintained. Also, a lock plate and the lock grooves are not destroyed by a forcible turn of the cylinder because the protruded portion of the cylinder advances into the lock grooves of the sleeve with the advancement of the sleeve.
In Patent Document 2 is described a cylinder lock in which a sleeve, a cylinder, tumblers, a driving member, a latch member, a release member and a spring are provided in a holder. The latch member is provided in the cylinder so as to be movable between an engaged position in which the cylinder and the driving member are connected and a separated position in which the connection is released. The release member is provided in the sleeve so as to be movable in radial directions, is generally shaped like a letter “U,” and moves the latch member to the separated position when the sleeve is turned relative to the holder. The spring presses the release member relative to the holder. On the release member is formed a protrusion that is to engage with a recess formed in the holder. When the sleeve is turned relative to the holder, the protrusion of the release member moves from the recess of the holder and the release member moves inward in a radial direction. Thus unlocking cannot be achieved with use of an unauthorized key because the latch member pressed by the moving release member moves in the radial direction and because the connection between the latch member and the driving member is released. That is, the use of an unauthorized key holds the driving member in a stationary state and causes the cylinder to turn. Therefore, a cylinder lock having a great resistance to destruction is obtained.
The cylinder lock disclosed in Patent Document 1, however, is configured so that a turn with an unauthorized key causes rearward movement of the sleeve with respect to the axial direction and slip of the cylinder, thereby preventing unlocking. a problem in that increase in a total length of the holder involves increase in the size of the cylinder lock as a whole.
The cylinder lock that is disclosed in Patent Document 2 and that performs the movement of the release member in the radial directions, thus the total length can be reduced in comparison with the cylinder lock disclosed in Patent Document 1. This cylinder lock, however, is increased in size, as a matter of course, because both the sleeve that is selectively connected to the cylinder and the driving member are positioned outside the cylinder and because the latch member and the release member are therefore required to be placed at a given interval with respect to the axial directions. In addition, the cylinder lock has a problem in that the mechanism for connecting the latch member and the release member complicates the structure and assembly of the cylinder lock.